1. Field of the Invention
The present invention relates to a pipe joint for opening and closing a flow passage through which a fluid flows, by connection and separation of a socket and a plug.
2. Description of the Related Art
Heretofore, when a socket and plug are connected to and separated from each other, a pipe joint has been utilized for automatically opening and closing a flow passage. By means of the pipe joint, since a valve body is caused to open and close automatically when the socket and plug are separated, the fluid flow passage is blocked and leakage of fluid is prevented.
For example, as shown in FIG. 10, in the pipe joint 1 disclosed in Japanese Patent No. 2732017, locking balls 2 are included on an outer circumferential part. The pipe joint 1 is equipped with a forward tubular portion 4 that slidably retains an operating sleeve 3 therein, and a rearward tubular portion 5 connected to a rear end part of the forward tubular portion 4. A socket body 6 is constructed from the forward tubular portion 4 and the rearward tubular portion 5. At the interior of the socket body 6, a valve mechanism 9 is provided. The valve mechanism 9 comprises a valve retaining member 7 which is formed with a cylindrical shape and a valve body 8 which is slidably inserted into the interior of the valve retaining member 7. A spring 10 is interposed between the valve body 8 and an end part of the valve retaining member 7, with the valve body 8 being biased by the spring 10 toward the side of the forward tubular portion 4. A first sealing ring 11 is mounted on an outer circumferential surface of the valve body 8. The first sealing ring 11 is capable of abutment against a valve seat 12, which is formed on the rearward tubular portion 5.
Further, a second sealing ring 13 is disposed between the rearward tubular portion 5 and the valve retaining member 7, and a third sealing ring 14, which is capable of keeping both members sealed in their retained state, is provided between the valve retaining member 7 and the valve body 8.
In addition, during a non-connected state of the forward tubular portion 4 with respect to the rearward tubular portion 5, the valve body 8 is advanced forward under a resilient action of the spring 10, whereupon the fluid passage 15 is blocked by abutment of the first sealing ring 11 against the valve seat 12. On the other hand, when the forward tubular portion 4 is connected, the front end of the forward tubular portion 4, which is inserted into the socket body 6, abuts against the end of the valve body 8, and the valve body 8, which is pressed by the forward tubular portion 4, is retracted in opposition to the elastic force of the spring 10. Additionally, through separation of the first sealing ring 11 away from the valve seat 12, the fluid passage 15 is opened and placed in a state of communication.
Further, as shown in FIGS. 11A and 11B, in the tube joint disclosed in Japanese Utility Model Publication No. 58-041430, a cylindrically shaped socket 20 is equipped with a valve body 22 therein, which is displaced under the resiliency of a compression spring 21. An end surface of the valve body 22 is disposed so as to be seatable on a valve seat 23 made of rubber, which is disposed on an inner wall surface of the socket 20. Additionally, a plug 24 is inserted from an end of the socket 20, wherein by the insertion of locking balls 25 provided in the socket 20 into an annular groove 26 of the plug 24, integral connection of the plug 24 and socket 20 is enabled.
Incidentally, in the conventional technique according to Japanese Patent No. 2732017, because first through third sealing rings 11, 13, 14 are provided respectively and individually, the number of parts making up the pipe joint 1 is increased, which leads to an increase in the number of assembly steps, as well as cost.
On the other hand, in the conventional technique according to Japanese Utility Model Publication No. 58-041430, when the plug 24 is inserted from an end of the socket 20, prior to abutment of the end of the plug 24 against the rubber valve seat 23, the valve body 22 is pressed by the plug 24 and separates away from the valve seat 23. Owing thereto, before sealing is carried out by the valve seat 23, the pressure fluid flows toward the side of the plug 24 from the socket 20, and as a result, pressure fluid tends to leak from between the socket 20 and the plug 24.
Moreover, with the plug 24 of the pipe joint, a structure is provided in which the plug 24 is inserted from the end of the socket 20, wherein a fluidtight condition is maintained between the socket 20 and the plug 24 by abutment against the valve seat 23. However, because an opposite reactive force is imposed with respect to the plug 24 from the valve seat 23 in a direction opposite to the direction of insertion thereof, resistance is encountered when the plug 24 is inserted, which makes the connection operation difficult.
Furthermore, at a time when the valve body 22 is seated, because a seating force is imparted with respect to the valve seat 23 from the valve body 22 in the same direction as the displacement direction of the valve body 22, resistance to pressure is reduced in the event that a high pressure is imparted with respect to the valve body 22.
Still further, since the valve body 22, which is utilized for switching the communication state of the pressure fluid, is arranged to cut across the fluid passage provided within the socket 20 and the plug 24, resistance is developed when the pressure fluid flows through the flow passage, accompanied by an increase in pressure loss.